In various operations conducted via underground wells, it is often advantageous to be able to gain information about one or more variables existing in the well bore or subterranean formation. In the arena of hydrocarbon exploration and production, example operations during which it may be beneficial to gain such information are drilling, cementing, completion, stimulation (including well treatment) and workover. The variables could be any measurable condition, parameter or property, such as one or more geometric dimension, the location of a particular object or geometric feature, temperature, pressure, flow, chemical composition, in-situ stresses in the well bore or formation, or the like. Note, the present disclosure is not limited by the type of operation, the target location in the well bore or formation or the type of variable.
In one example in the hydrocarbon recovery arena, it is often of significant benefit to learn about the geometry of an area within an underground well or subterranean formation, such as the location or dimensions of propped hydraulic fractures. Hydraulic fracturing is a widely used process for stimulating oil and gas wells and which typically involves injecting fluid into the well bore at a higher pressure than the surrounding reservoir pressure. The higher pressure of the injected fluids causes the formation to fracture, exposing the surface area through which oil or gas may flow.
Once a hydraulic fracture is formed, proppant is typically delivered into the fracture during well treatment to effectively increase the conductivity of the fracture and provide a flow path of hydrocarbons between the reservoir and the producing well bore. Proppants ensure the created flow path remains open and conductive after the treating pressure is relieved. Proper placement of the proppant is often considered one of the most critical facets of fracture stimulation. The propped fracture area is believed to directly correlate with stimulated well potential and productivity, whereby the larger the propped fracture, the more productive the well. It is thus typically advantageous to know the location and/or dimensions of propped fractures or proppant packs within conductive fractures. For example, knowledge of the location of proppant in fractures and/or the dimensions of propped fractures can, in some instances, assist in optimizing and improving fracturing efforts and proppant distribution, well placement and production strategies.
Existing techniques for mapping or visualizing underground geometries (e.g. micro-seismic fracture mapping, tilt-meter fracture mapping, use of tracers) are believed to have one or more limitations. For example, some of these techniques provide information on only one dimension or feature (e.g., length, height, depth or azimuth). For another example, some of these techniques only provide information about the formation in close proximity to the well bore. For other examples, some current technologies require the use of one or more offset wells, which may dramatically increase costs, and/or radioactive material, which may be environmentally damaging.
It should be understood that the above-described discussion is provided for illustrative purposes only and is not intended to limit the scope or subject matter of this disclosure, the appended claims or the claims of any related patent application or patent. Thus, none of the appended claims or claims of any related patent application or patent should be limited by the above discussion or required to address, include or exclude the above-cited examples, features and/or disadvantages merely because of their mention above.
Accordingly, there exists a need for improved systems, apparatus and methods capable of providing information about one or more variables in an underground well or subterranean formation having one or more of the attributes, capabilities or features described below or in the subsequent sections of this disclosure; provides information about one or more variable existing in a well bore, annulus or subterranean formation; provides such information during at least one among drilling, cementing, completion, stimulation and workover; provides such information without the transmission of signals to the target location; provides information about one or more geometric dimension, the location of a particular object or geometric feature, temperature, pressure, flow, chemical composition or in-situ stresses in an underground well, subterranean formation or hydrocarbon reservoir; can be used to improve well stimulation operations and well performance planning; provides information about the location of proppant disposed within a propped fracture or other area; provides multiple dimensions of an underground geometric feature; provides signal generating devices at one or more target location(s) to accomplish one or more of the above; uses signal generating devices that capture, generate or provide energy in-situ for transmitting one or more signals; incorporates nano-devices capable of generating energy and/or transmitting signals; uses piezoelectric signal generating devices; uses signal generating devices that include sound generating material capable of emitting detectable sound waves from a subterranean location; does not require the use of offset wells or radioactive materials; is reliable; is easy to implement; requires minimal retrofitting of existing equipment; is cost-effective.